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Forum: Biostatistics

Epidemiology and biostatistics, public health research. GLM, logistic regression, survival analysis, clinical trials.

  1. Dunnett's test for longitudinal data

    Dear Stats Folk, I have a one Control group and one patient group. I have measurements on Controls at one time point, while I have a single...

    Started by Jim Corbett‎, 04-30-2013 05:22 PM
    dunnett's, t-test
    • Replies: 0
    • Views: 2,481
    04-30-2013, 05:22 PM Go to last post
  2. pairwise comparison regardless effect

    Hi there, I want to do a pairwise comparison of gene expressions (continuous values) before and after treatment of a group of patients regardless...

    Started by bambam‎, 04-29-2013 04:23 AM
    • Replies: 2
    • Views: 1,398
    04-30-2013, 04:25 AM Go to last post
  3. Help needed for the interpretation of ANOSIM results in Primer

    As new to biostatistics I would appreciate some help on the interpretation of ANOSIM results in Primer. Thank you!!...

    Started by Koula‎, 04-29-2013 09:02 AM
    • Replies: 0
    • Views: 4,324
    04-29-2013, 09:02 AM Go to last post
  4. Time*predictor interaction term for longitudinal study analysis

    Hello Forum, Currently I am analyzing results of longitudinal study evaluating the effects of possible dichotomous predictor on continious outcome...

    Started by DSSS‎, 04-28-2013 10:07 PM
    • Replies: 0
    • Views: 3,680
    04-28-2013, 10:07 PM Go to last post
  5. Compare the variations of bacterial species between test groups

    Hello, I have been scratchiong my head for a few days on this problem, which should be pretty simple. I really hope someone can point me in the...

    Started by Koblenz‎, 04-28-2013 10:46 AM
    • Replies: 0
    • Views: 2,295
    04-28-2013, 10:46 AM Go to last post
  6. Odds ratios less than 1, how to make interpretation ?

    Hello all, How do I make interpretation of odds ratio equal to 0.02, given from a logistic model with a binary outcome and let's say 2 treatments...

    Started by NN_STAT‎, 04-27-2013 07:51 AM
    • Replies: 5
    • Views: 36,784
    04-28-2013, 12:33 AM Go to last post
  7. Wide CI for odds ratio

    Hello all, I ran a model that yields odds ratio, like the logistic regression does. I have received a very wide CI. To illustrate the reason,...

    Started by NN_STAT‎, 04-24-2013 08:12 AM
    • Replies: 5
    • Views: 4,068
    04-27-2013, 11:50 PM Go to last post
  8. Question More than 2 outcome (categorical), what is the statistical test?

    Hello everyone! If I have an outcome (dependent variable) is 3 outcomes (Scale of measurement: categorical/nominal) and the interdependent...

    Started by Halah‎, 04-26-2013 11:58 AM
    • Replies: 4
    • Views: 2,996
    04-26-2013, 12:32 PM Go to last post
  9. Kaplan-Meier and log-rank analysis

    Question about Kaplan-Meier analysis and log rank. I am currently working on a project using the National Cancer Institute's SEER database. A lot of...

    Started by savant624‎, 04-24-2013 06:03 PM
    • Replies: 0
    • Views: 2,653
    04-24-2013, 06:03 PM Go to last post
  10. A T test question

    This is a question on presenting the result of the effectiveness of weight loss program. There is only one group of subject and two time point ( pre...

    Started by kolokicy‎, 04-22-2013 09:45 PM
    • Replies: 4
    • Views: 1,844
    04-23-2013, 04:45 PM Go to last post
  11. Lightbulb Design Issue: Retrospective Cohort or Case Control?

    Good Morning! I am currently trying to decide which approach to my research question is best. I am using a large data set from a state agency. The...

    Started by christinarn2000‎, 04-11-2013 11:54 AM
    • Replies: 5
    • Views: 3,083
    04-22-2013, 09:18 PM Go to last post
  12. Testing the assumption of linearity in a multi-level logistic regression analysis

    Hello all! I am working on a multi-level logistic regression (Binary Outcome) model and am trying to finding the best way to check the assumption of...

    Started by Klh449‎, 04-19-2013 08:17 PM
    • Replies: 4
    • Views: 7,182
    04-22-2013, 01:24 PM Go to last post
  13. too high CV

    Hello friends, when i am analysing my data using ANOVA, i came up with a very large cv(55) is there any means to lower it? my design is 4x5 CRD with...

    Started by jamesbiot01‎, 04-14-2013 03:07 AM
    • Replies: 3
    • Views: 2,855
    04-20-2013, 08:37 AM Go to last post
  14. Test if non-negative measurements are significantly different from 0 (5 replicates)

    I have measurements basically indicating how much a gene is used in specific individuals. The way you do this is by counting how much gene product...

    Started by Rubber‎, 04-19-2013 04:41 PM
    • Replies: 1
    • Views: 2,792
    04-19-2013, 06:12 PM Go to last post
  15. Non-inferiority Cox model

    Hello, I am trying to design a study in which the primary endpoint is time to event. Due to some constraints, the study needs to be a...

    Started by NN_STAT‎, 04-17-2013 06:33 AM
    • Replies: 0
    • Views: 1,738
    04-17-2013, 06:33 AM Go to last post
  16. Variable prediction

    Hi everyone, I'm currently doing work with morphometry, working with data I've collected and with an already existing database. At the moment I'm...

    Started by PeterAlex‎, 04-05-2013 06:54 AM
    • Replies: 1
    • Views: 1,256
    04-17-2013, 05:21 AM Go to last post
  17. How to Report Dunnett MCT?

    Hello, How do I properly report an ANOVA followed by Dunnett's MCT in APA format? Below is the report minitab generates for Effects of Dose on...

    Started by sudds779‎, 04-16-2013 09:59 AM
    • Replies: 0
    • Views: 2,662
    04-16-2013, 09:59 AM Go to last post
  18. Question frequency of heterozygous allele between two groups

    I am sorry I am not statistician but I have a very simple (maybe stupid:)) question. I have case group of 4460 and controls of 5085, P value is...

    Started by manu26‎, 04-12-2013 04:47 AM
    allele, case control, frequecny
    • Replies: 0
    • Views: 1,231
    04-12-2013, 04:47 AM Go to last post
  19. control of type I error?

    Hello forum, I am seeking your advise. Here is the problem: In a clinical trial, we will collect MRI imaging data from each patient...

    Started by teddyofphilly‎, 04-11-2013 01:52 PM
    • Replies: 3
    • Views: 886
    04-11-2013, 02:24 PM Go to last post
  20. Correct statistical test to compare pre and post questions (dummy variable)

    Hi friends, What is the correct statistical test to compare a group who was tested in two points in time (pre and post) The same people. I have...

    Started by Marvin85‎, 04-11-2013 08:41 AM
    dummy variable ttest, statistical test, ttest
    • Replies: 2
    • Views: 2,153
    04-11-2013, 08:55 AM Go to last post
  21. Exclamation [SPSS - Binary logistic test - Interaction (moderator) ]

    DV: dichotomous (0 = show, 1 = no-show) IV (covariates): Geslacht = Gender dvd_week = Day of the week Gender (0 = females, 1 = males)...

    Started by Kelvin86‎, 04-10-2013 04:06 PM
    • Replies: 3
    • Views: 1,982
    04-10-2013, 06:15 PM Go to last post
  22. Wink Simple question concerning a population with known distribution and a smaller sample

    Hello, I have a complete population consisting of 6587 individuals (genes) and for each individual I have a distance value. These distance...

    Started by devking‎, 04-10-2013 01:59 PM
    • Replies: 0
    • Views: 1,340
    04-10-2013, 01:59 PM Go to last post
  23. Comparing Qualitative Integer Scores: Non-parametric alternative to ANOVA needed?

    I am trying to analyze data from the longitudinal qualitative scoring of knee joints to measure differences in disease severity by a number of...

    Started by dinsdale‎, 04-10-2013 10:09 AM
    • Replies: 0
    • Views: 1,323
    04-10-2013, 10:09 AM Go to last post
  24. Mann-Whitney U and Bonferroni Correction

    I recently presented some work in my department in which my colleagues and I had applied a Mann-Whitney U test for multiple pairwise comparisons. We...

    Started by Zachariah‎, 04-05-2013 01:27 PM
    bonferroni correction, mann-whitney u, non-parametric
    • Replies: 3
    • Views: 12,580
    04-08-2013, 09:31 AM Go to last post
  25. Removing interaction effect on 2-way ANOVA?

    Hello, I've run a 2 way ANOVA of my research results and got these 3 p-values: A=0.001, B=0.069, and A*B=0.167. My professor now wants me to remove...

    Started by Lizzbee‎, 04-07-2013 08:44 PM
    anova, data, interaction, p-value, sigmaplot
    • Replies: 1
    • Views: 4,764
    04-07-2013, 09:02 PM Go to last post
  26. multivariate Cox regression, ordinal variable as dummy variables, and p value

    I'm trying to understand a paper on kidney cancer research. The study uses a multivariate Cox regression. The outcome variable is death/no death from...

    Started by KidneyBoy‎, 04-05-2013 02:27 PM
    • Replies: 0
    • Views: 2,794
    04-05-2013, 02:27 PM Go to last post
  27. How do I show something is an 'independent variable'?

    Please help. I am totally confused about how to show that something is an independent risk factor. I.e. in a cohort study: Group A (n=1000) -...

    Started by RoseMarie‎, 04-02-2013 04:19 PM
    independent risk factor, risk ratio
    • Replies: 2
    • Views: 1,827
    04-03-2013, 01:04 AM Go to last post
  28. Goodness-of-link test

    Hello, I am trying to test whether my choice of link function is correct using the goodness-of-link test. So, firstly since I am testing the...

    Started by GTaiko‎, 04-02-2013 10:31 PM
    • Replies: 0
    • Views: 2,505
    04-02-2013, 10:31 PM Go to last post
  29. probably any easy question for the stat inclined (not me)

    Hi all, A population of patients were tested for 3 viruses and have a variety of symptom questions associated. For example: ...

    Started by bdiddy‎, 04-01-2013 06:28 PM
    • Replies: 1
    • Views: 1,309
    04-02-2013, 07:10 AM Go to last post
  30. Smile Sampling Size determination

    Hello All I have a population of 22000 individuals. I wanted to mesure a mean value of a specific parameter. for this purpose I randomly tested...

    Started by sirszimansky‎, 03-31-2013 02:05 AM
    • Replies: 0
    • Views: 1,188
    03-31-2013, 02:05 AM Go to last post
  31. Working out risk factors for a medical complication?

    Hi All - HELP! I have a large dataset on women in labour, and I'm interested in finding out risk factors for a particular complication of labour....

    Started by obsreg‎, 03-24-2013 04:11 PM
    disease, logistic regression, odds ratio, relative risk
    • Replies: 2
    • Views: 1,535
    03-29-2013, 08:19 AM Go to last post
  32. How to present data after Holm-Bonferroni Correction

    Hi all, I am manually using Holm-Bonferroni method to correct my data as I can't find a way to do it using software. As the data is relatively...

    Started by artery‎, 03-19-2013 05:48 AM
    bonferroni, holm
    • Replies: 1
    • Views: 5,013
    03-28-2013, 08:20 PM Go to last post
  33. Testing significance of frequencies by position of nucleotide pairs

    Hi all, I have a set of frequencies for each of the 16 possible nucleotide pairs at a given position in a sequence. I want to test whether any of...

    Started by xaio21‎, 03-28-2013 06:53 PM
    • Replies: 0
    • Views: 2,644
    03-28-2013, 06:53 PM Go to last post
  34. Sample size with G power

    Hello I ran some sample size calculations using Gpower, in order to find the minimum required sample size for the Fisher exact test, since I need...

    Started by NN_STAT‎, 03-22-2013 09:21 AM
    • Replies: 2
    • Views: 4,612
    03-27-2013, 09:37 PM Go to last post
  35. one way ANOVA for rank data?

    I was recently reading up on nonparametric alternatives to one way ANOVA and came across a description of ANOVA on rank data...

    Started by Disvengeance‎, 03-27-2013 03:02 PM
    • Replies: 0
    • Views: 3,851
    03-27-2013, 03:02 PM Go to last post
  36. Comparing 2 different pop sizes

    Hi, I am running up against some problems in my stats analysis. Please can anyone give me a hand on this... I have data on Emergency Department...

    Started by PedroR‎, 03-27-2013 06:54 AM
    • Replies: 0
    • Views: 1,486
    03-27-2013, 06:54 AM Go to last post
  37. Hypothesis testing for very large sample sizes

    Hello everyone, I am trying to figure out which hypothesis test is best for my research. I have two groups of patients (Group 1, n = 726,314...

    Started by Bboggess‎, 03-26-2013 03:01 PM
    • Replies: 1
    • Views: 1,170
    03-26-2013, 03:30 PM Go to last post
  38. reescaling ?

    Hello to all. I'm analizyng a data composed by several paired observations. The first observation is non treated that is the baseline of signal....

    Started by piruvato‎, 03-26-2013 02:05 PM
    • Replies: 0
    • Views: 1,398
    03-26-2013, 02:05 PM Go to last post
  39. Comparing groups-carbohydrate microarray

    I have a large dataset representing levels of binding of fluorescently-labelled bacteria to multiple carbohydrates on a microarray, comprised of 88...

    Started by miromar‎, 03-22-2013 05:32 PM
    • Replies: 1
    • Views: 1,212
    03-25-2013, 06:00 AM Go to last post
  40. Flight times of insects

    I'm researching the flight times of a wasp in the southeast. The trap catches occurred in 09,20,11, and 12. However, these were done by three...

    Started by jhartsho‎, 03-09-2013 11:26 AM
    2 Pages
    1 2
    • Replies: 16
    • Views: 3,612
    03-23-2013, 08:58 PM Go to last post
  41. Comparing ratios between groups using population estimates with confidence intervals

    Based on two national population surveys, I have estimates of rates of event A and event B (with 95% confidence intervals) by age category and...

    Started by Aquinna‎, 03-20-2013 08:00 AM
    • Replies: 2
    • Views: 1,620
    03-20-2013, 01:44 PM Go to last post
  42. How do analyze the error bars of a Standard Error statistical test?

    Hi I'd be really appreciative if anyone might be able to help me. I'm studying biology at a foundation level and have recently been introduced to...

    Started by ggdf‎, 03-19-2013 02:33 PM
    • Replies: 2
    • Views: 5,845
    03-19-2013, 08:51 PM Go to last post
  43. Using G*power to calculate a priori sample size

    My experimental design is very simple: test cells at 0, 50, and 100 uM concentrations of drug and count for toxicity. Using G*power, I'm pretty...

    Started by ubiquitous‎, 03-19-2013 11:21 AM
    • Replies: 0
    • Views: 3,966
    03-19-2013, 11:21 AM Go to last post
  44. Predicted probabilities for discrete-time event history analysis

    Does anyone know how to calculate predicted probabilities for a discrete-time event history analysis? Just in case the term "predicted...

    Started by ziotstats‎, 03-18-2013 11:51 AM
    discrete-time, event history analysis, predicted probabilities
    • Replies: 0
    • Views: 1,617
    03-18-2013, 11:51 AM Go to last post
  45. multidimensional relationship inter/intra

    Dear all, I hope that my thread does not overlap other posts but I am not sure about the keywords to search this forum. Here is my problem, I...

    Started by descostes‎, 03-18-2013 07:50 AM
    • Replies: 2
    • Views: 1,344
    03-18-2013, 09:30 AM Go to last post
  46. Relationship between sample mean and sample survival probability

    I am not sure if this question is very naive, but I was wondering if there is a relationship between sample mean and sample survival probability. For...

    Started by Blain Waan‎, 03-17-2013 10:17 AM
    biostatistics, survival analysis
    • Replies: 2
    • Views: 1,363
    03-17-2013, 10:11 PM Go to last post
  47. Simulation of remission and after remission times under specific conditions

    This is basically a data generation problem. Say, t is an exponential lifetime with mean two years. tr is the remission time and ts is the after...

    Started by Blain Waan‎, 03-17-2013 10:12 AM
    simualtion, simulated_data, simulation study, survival analysis
    • Replies: 1
    • Views: 1,300
    03-17-2013, 10:58 AM Go to last post
  48. •Comparing groups - which test should I use(t-test or ANOVA)

    The general infomation is: We have 6 kinds of material and have 4 group for each material now(please see the attached table) we cut one tooth to...

    Started by xiaohui‎, 02-23-2013 06:07 AM
    • Replies: 6
    • Views: 46,022
    03-17-2013, 05:43 AM Go to last post
  49. Sample size for rare events

    Hello I need to calculate the sample size for a study with the primary objective being to test the efficacy of a new treatment. The failure rate...

    Started by NN_STAT‎, 03-15-2013 08:53 AM
    • Replies: 2
    • Views: 5,456
    03-16-2013, 10:43 AM Go to last post
  50. Covariate imbalance and restricted randomization

    Dear all, I'm involved in a cluster-randomized clinical trial with 20 clusters and 2 treatment arms, intervention and control. We would like to...

    Started by tcbiostats‎, 03-16-2013 10:27 AM
    clinical trials, covariate imbalance, covariates, randomization, restricted randomization
    • Replies: 0
    • Views: 1,010
    03-16-2013, 10:27 AM Go to last post
  51. Two therapies in two separate populations over time

    Good Evening, I would appreciate any input on the following problem, I have searched around the web to see if I can find a more effective...

    Started by blindv‎, 03-15-2013 08:34 PM
    • Replies: 2
    • Views: 1,847
    03-16-2013, 09:36 AM Go to last post
  52. calculating % difference

    Hi all, I need your help in solving this problem, my data looks like this I.D Var1 1 AA 2 AA 3 AA 4 AA 5 AG 6 ...

    Started by Genetist‎, 03-13-2013 11:19 AM
    • Replies: 4
    • Views: 1,491
    03-16-2013, 12:17 AM Go to last post
  53. Compare independent gene lists after statistical test (limma)

    Dear all, I have a general question about the statistical analysis approach that I intend to use, which basically boils down to "is this feasible to...

    Started by bontus‎, 03-14-2013 10:20 AM
    • Replies: 0
    • Views: 1,273
    03-14-2013, 10:20 AM Go to last post
  54. How do cell biologists perform power of analysis?

    Often times you only see POA for clinical studies or studies involving humans. However, I'm under the impression that ANY scientist should perform...

    Started by ubiquitous‎, 03-12-2013 09:10 PM
    • Replies: 0
    • Views: 1,121
    03-12-2013, 09:10 PM Go to last post
  55. Analysing circular (angular) data - how to find significant differences?

    Dear users, this is a problem from my PhD thesis. I am grateful for suggestions. I have measured angular data from several individuals, each...

    Started by DEW‎, 03-06-2013 05:33 AM
    2 Pages
    1 2
    • Replies: 18
    • Views: 5,312
    03-12-2013, 07:23 AM Go to last post
  56. Denominator in rate

    Hi! This isn't so much a statistical question as it is just figuring out the appropriate dates in which to include cases into a denominator for a...

    Started by jamesmartinn‎, 03-10-2013 06:54 PM
    • Replies: 0
    • Views: 3,480
    03-10-2013, 06:54 PM Go to last post
  57. p value of 0.000 on SPSS

    I am using SPSS to define relationship between two variables. Previous research has indicated a significant relationship between them. Spearman...

    Started by viciousorphan‎, 03-10-2013 01:13 AM
    • Replies: 6
    • Views: 58,812
    03-10-2013, 03:16 PM Go to last post
  58. Which statistical method will be best for these variables?

    I am using three variables in my paper. One is barthel index which is scored out of 100. It measures funtional disability of patients.The lower the...

    Started by viciousorphan‎, 03-10-2013 09:23 AM
    • Replies: 0
    • Views: 2,914
    03-10-2013, 09:23 AM Go to last post
  59. comparing multiple observations with each variable and expressing as % match

    Hi dear all, Here i want to compare 5854 observations (plant I.D) with each variables (44) here (marker alleles). For example if all observations...

    Started by Genetist‎, 03-09-2013 07:14 AM
    • Replies: 0
    • Views: 1,345
    03-09-2013, 07:14 AM Go to last post
  60. Relative Risk in logistic regression

    Hi all, I am very grateful to all those who write to me 1) how i can obtain relative risk (risk ratio) in logistic regression in R. 2) how to...

    Started by aminreza‎, 01-30-2013 06:36 AM
    • Replies: 3
    • Views: 2,653
    03-07-2013, 01:17 AM Go to last post

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